Stretch To with Copy Location bone constraints not working properly
You need to do two things here, uncheck connected on each bones' parenting as it messes with the copy locations, and then set the bone tips to the same position as the empties in edit mode before resetting the stretch to length.

Uncheck this checkbox on each bone:



I would suggest making the stretch to target the next bone rather than the empty, as that will make it easier to set the rest positions/lengths with reset.

Fixed blend: